Audi RS3 Unitronic downpipe and midpipes

Best Audi RS3 Mods Guide

Chandler Stark

Meet Chandler

Chandler is an automotive history expert with a Master’s Degree in American history. He enjoys working on and modifying cars, including his previous Subaru WRX and his current MK7.5 GTI, which is tuned through Equilibrium Tuning. In addition, Chandler also loves classic American muscle and is a frequent attendee of local car shows. His dedication and passion for the automotive industry shows through in his high-quality and intuitive content for VW Tuning readers.

Among Audi enthusiasts, the RS3 has long been one of the top performance offerings. Featuring a turbocharged 2.5 inline-five cylinder engine, for the 2023 model year the RS3 puts down a solid 401 horsepower and 369 lb-ft of torque. That’s good for a zero to 60 mph time of just 3.6 seconds, and a ¼ mile in 11.8 seconds @ 117 mph. It’s definitely fast, but compared to the twin-turbo 2.9 liter V6 inside the RS5 with 444 horsepower, the RS3 feels lacking. That’s why today we’re looking at the top Audi RS3 mods to increase performance. Read on to find out how to crack 500 wheel-horsepower with the best RS3 mods. 

Audi RS3 and Engine Info

Audi first released the RS3 Sportback in 2011, where it featured a TFSI turbocharged, 2.5 liter inline-five engine making 340 horsepower and 330 lb-ft of torque. The first generation RS3 didn’t last very long, but Audi soon brought it back in 2015, and it has been a mainstay ever since, except 2021 when it was on a brief hiatus. Today, the Audi RS3 still uses the same engine as it did back in 2011, but it now pumps out 401 horsepower and 369 lb-ft of torque. 

The RS3 uses a seven-speed dual-clutch automatic transmission, and unfortunately a manual is not an option. In addition, all RS3s use Audi’s Quattro all-wheel drive system. The TFSI engine uses a compacted graphite iron (CGI) block, aluminum alloy cylinder head, die-forged steel crankshaft, forged steel factory cracked connecting rods, and cast aluminum alloy pistons. It is a 20-valve engine, with four-valves per cylinder, dual-overhead camshafts (DOHC), and variable valve timing. 

The 2.5 TFSI uses direct injection fueling for improved performance and reduced emissions. It also uses port injection in conjunction, which reduces carbon buildup and allows for increased fueling. The turbo runs at a maximum of about 17-18 PSI of boost, depending on the atmospheric and environmental conditions. The RS3 has a front-mount, air-to-air intercooler, and uses three catalytic converters in the exhaust: one primary and two secondary. Enthusiasts widely consider the 2.5 TFSI engine to be extremely reliable and a fantastic power plant for modding. 

Audi RS3 Mods Engine Power Limits

Before we get into the top RS3 mods recommendations, it’s important to talk about the power limits of the 2.5 TFSI. From the factory, the engine already spits out an impressive 401 horsepower and 369 lb-ft of torque as of the 2023 model year. From such a small engine that’s already pretty substantial, and is a big reason the turbo has to run so much boost (17-18 PSI).

When the 2.5 TFSI is left stock, most people consider it to be a relatively reliable engine. However, once you start adding some RS3 mods to the engine, things start to change. For the most part, the generally accepted limit for the OEM connecting rods and pistons is about 500-550 wheel-torque. That equates to roughly 600-650 lb-ft of torque at the crank. 

Past 550 wheel-torque, the connecting rods tend to bend and the pistons tend to break. Stock, the RS3 puts down about 340 wheel-horsepower and 320 wheel-torque, so 500+ lb-ft of torque to the wheels is pretty significant. If you plan on approaching 550 wheel-torque, you’ll want a completely built bottom end with forged connecting rods (stronger than stock) and forged pistons, along with head studs. 

Audi RS3 Supporting Mods

Another important topic to dive into when looking at RS3 mods are supporting mods. Besides making sure the engine is built internally, you also need to make sure the spark and fueling are up to the task of a modded engine. Once you upgrade the downpipe or decide to go with E85 fueling, you need to upgrade both the spark plugs and fueling system. 

Upgraded spark plugs should be one-step colder than stock to keep down cylinder temperatures and pressure. Upgrading the port injection is a bit trickier, but is cheaper, easier, and more reliable than upgrading the direct injection system. The Unitronic MPI Injector Upgrade Kit is the most used port injection upgrade, and is necessary for running ethanol blends or an upgraded exhaust.

Audi RS3 Stages for Modding

When looking up the Audi RS3, you’ve probably seen things like Stage 1, Stage 1+, Stage 2, etc.. These are just shorthand ways of listing different mods for the RS3. Some manufacturers have slightly different definitions, but here are the usual interpretations of the stages of RS3 modding.

Stage 1 is generally considered just an ECU tune, and Stage 1+ typically refers to an ECU tune and an upgraded intake. Usually, Stage 2 refers to an ECU tune, upgraded intake, upgraded downpipe/midpipes, and an upgraded intercooler. Stage 3 refers to everything from stage 2 with the addition of a turbo upgrade.

Power-wise on 93 octane, Stage 1 is roughly 475-500 horsepower and 450-500 lb-ft of torque, and Stage 1+ is 500-525 horsepower and 475-515 lb-ft of torque. Stage 2 is roughly 550 horsepower and 525 lb-ft of torque. Adding ethanol will easily show gains of an additional 75-100 horsepower and 100-150 lb-ft of torque on top. With a Stage 2 tune and ethanol, you can expect to make roughly 500 wheel-horsepower with the RS3. 

Top 6 Audi RS3 Mods

Our top 6 Audi RS3 mods are:

  • Intercooler Upgrade
  • ECU Tune or JB4
  • E85 Flex-Fuel
  • Upgraded DogBone Mount
  • Downpipe/Midpipe Upgrade
  • Upgraded Intake and Turbo Inlet

1) Best Audi RS3 Mods: Intercooler Upgrade

STM Intercooler for Audi RS3 2.5 TFSI

The first RS3 mod we recommend looking at is an upgraded intercooler. The intercooler is one of the most important parts of any turbocharged system, and the 2.5 TFSI is no different. The purpose of the intercooler is to cool down the charged air or boost after it exits the turbo. Turbochargers run off exhaust gas, and they also compress air, both of which generate a ton of heat. Hotter air has less oxygen than colder air, so it makes less power. In addition, hotter air leads to increased cylinder temperature and cylinder pressure, which leads to detonation and pre-ignition.

The RS3 intercooler is an air-to-air, front-mount intercooler, and it sits just behind the grille. Unfortunately, even though it is a front-mount, the OEM intercooler is woefully undersized, even for a completely stock RS3. The OEM intercooler is prone to heat soak after only limited use, meaning it is no longer able to sufficiently cool the charged air. If you add any mods, the OEM intercooler will be practically useless. 

Even tuning usually increases the boost, which the stock unit just can’t properly handle. It’s even worse if you live in a hot climate like Arizona or Texas. In addition, an aftermarket intercooler will weigh 10-20 pounds less than stock, which is great weight savings right where you want it. That’s why we recommend it as our first mod. 

Best RS3 Intercooler Upgrades

There are two RS3 intercooler upgrades we recommend: either the STM Tuned RS3 front-mount intercooler or the Iroz RS3 front-mount intercooler. Both the STM and Iroz intercoolers are direct fit for the stock unit, and are completely plug and play. They will add 15-25 horsepower on a completely stock car, and even more with tuning. Upgraded intercoolers will also help the RS3 to make repeated runs without losing power, especially in the summer. 

Both the STM and Iroz intercoolers use Garrett cores, with the STM core rated to 1,000 horsepower and the Iroz core to 800 horsepower. The Iroz unit is considerably more expensive than the STM, but it also looks a bit nicer. They will both perform pretty much the same until you really start making lots of horsepower, at which point the larger core of the STM might be more beneficial.

2) Best RS3 Mods: Tuning for ECU/TCU and JB4 Piggyback

After you upgrade the RS3 intercooler, your next step is undoubtedly to get custom RS3 ECU and TCU tuning. The ECU is the engine control unit, and the TCU is the transmission control unit. Tuning the ECU and TCU are hands down the best ways to add horsepower and torque and improve shifting. On the Audi RS3, you can add 75 horsepower and 100 lb-ft of torque with just tuning. That’s almost a 20% horsepower increase and more than 25% torque increase without any bolt-on mods. Pretty impressive. 

Flash tunes are incredibly easy to install and can be done with just a few minutes and a handheld device. Flash tunes have pre-loaded engine software that optimizes engine parameters like ignition timing, air-to-fuel ratios, boost pressure, and valve timing, to increase performance. Piggyback tuning is the other option. Instead of installing software onto the ECU/TCU, piggyback tunes physically plug into the ECU/TCU and manipulate the signals before they reach the engine. This has the same effect as tuning, but is more untraceable. 

Best RS3 Tuning Options

For flash tuning, the best RS3 tuners are Unitronic RS3 Tuning and EQTuning RS3 Tuning. Both Unitronic and EQTuning have fantastic reputations for the Audi and Volkswagen platforms, and they are capable of delivering outstanding tunes. They are both capable of tuning anything from completely stock engines all the way up to ethanol-flowing turbo-swapped RS3s. Personally, I went with EQTuning for my 2.0 TSI-powered GTI, and they were fantastic to work with. EQT is generally cheaper than Unitronic. 

For piggyback tunes, the JB4 for RS3 from Burger Tuning is the standard for the RS3. The JB4 is most well known inside the BMW and Kia communities, but their unit for the RS3/TTRS is fantastic. With the JB4 and other supporting mods, you can add as much as 100 wheel-horsepower and 100 wheel-torque. 

3) Audi RS3 Ethanol E85 Tuning and Flex-Fuel Kit

Along with tuning, upgrading the Audi RS3 to run on flex-fuel is going to be the biggest bang for your buck. Ethanol is a great way to add power because it has such a high octane rating. Compared with standard 91-93 octane gas, full E85 has an octane rating of 104, while E60 is still in the mid-to-upper 90s. 

Higher octane allows for the ability to run more ignition timing, more boost pressure, and leaner air-to-fuel ratios without encountering detonation or pre-ignition. Compared with standard 91-93 octane fuel, you can gain an additional 100 horsepower and torque with just E60 fueling.

In addition to ethanol tuning, there is also the option for flex-fuel tuning. Flex-fuel is great for those who do not have regular access to an E85 pump during their average driving and need to occasionally fill up with pump gas. Flex-fuel tuning involves the use of a flex-fuel sensor, which reads the ethanol content of the fuel. With a flex-fuel, the car will adjust the aggressiveness of the tune based on the ethanol content, with more ethanol leading to more powerful mapping. 

A flex-fuel sensor and tune allows you to run any combination of fuel from pump gas all the way to E60 (most tuners don’t tune past E60 levels). This way, if you want to get the full brunt you can get only ethanol, or if you don’t have the option, you can get a few gallons of pump gas and will still be able to boost when you want.

Best RS3 Flex-fuel Kits

By far, the best RS3 flex-fuel kit is the Flex-it RS3 Flex-Fuel Kit. This is a completely plug-and-play kit that easily allows you to read the ethanol content of your fuel. It is compatible with the JB4 and most custom tuners are able to tune with it. The Flex-it kit has an integrated smartphone app that connects via bluetooth, allowing you to view the ethanol content from your phone. 

4) Best RS3 Mod for Handling: DogBone Upgrade

Now that we’ve looked at making the engine more powerful, you need to think about upgrading the handling. The Audi Quattro AWD system is great, but it struggles to put power down to all four wheels once you start modding. Many modded RS3 owners notice wheel-hop, especially from a dig, when adding even a modest amount of horsepower.

The dogbone mount, or the pendulum mount as it is also known, is by far the best RS3 mod for suspension. The dogbone mount sits in the subframe under the RS3, and its job is to keep the engine in place. However, the OEM mount allows for way too much engine movement. The lurching forward and backward of the motor under hard acceleration is terrible for traction, and results in wheel hops and can also hurt shifting.

The dogbone mount consists of both the actual steel mount and the bushing inside. You can choose to upgrade either one or the other, but we suggest the full mount and bushing upgrade for the best performance.

Best RS3 DogBone Upgrade

By far, the best RS3 dogbone upgrade is the Unitronic RS3 DogBone Mount. The Unitronic unit uses T7075 billet aluminum for the mount and polyurethane for the bushings. Many consider the Unitronic dogbone mount the standard for the RS3, and it’s hard to disagree. There is both a race version and a street version of the Unitronic, with the race version being a bit stiffer. 

5) RS3 Downpipe and Midpipe Upgrades

Getting back to the engine, after tuning the best RS3 mods are upgrading the downpipe and midpipes. The downpipe is the part of the exhaust that connects directly to the turbocharger, and the midpipes run from the downpipe back to the cat-back. The 2.5 TFSI in the RS3 has a bit of a unique downpipe and midpipe setup. 

On the stock exhaust, the catalytic converter in the downpipe is located as close to the turbocharger connection as possible. From the primary cat, the downpipe splits into two smaller pipes. The midpipes connect to these pipes and each has a smaller secondary cat. You have the option of replacing either the downpipe cat, the midpipes’ cats, or both, on the RS3. Replacing the OEM cat with a high-flow cat will substantially increase exhaust flow and reduce back pressure. 

Upgrading the downpipe is known as “Stage 2” on the RS3. With a downpipe, you can easily add an additional 50+ horsepower with tuning. Swapping the midpipes won’t reduce the back pressure as much since they are further downstream and the cats are smaller. However, you can still add 30+ horsepower with upgraded catless midpipes. 

Best RS3 Downpipe and Midpipes Upgrades

Audi RS3 Unitronic downpipe and midpipes
Audi RS3 Unitronic downpipe and midpipes

We have a few different recommendations for you in terms of downpipe and midpipe upgrades. The most popular RS3 downpipes are the IE RS3 Two-piece Downpipe and the Unitronic RS3 Downpipe. They do however have pretty radically different designs. The Unitronic RS3 downpipe mimics the style of the OEM downpipe, with one large pipe splitting into two smaller ones (pictured above with midpipes). The IE RS3 downpipe on the other hand consists of one larger diameter tube the whole way. 

The cat placement is also different, as the Unitronic places it in the OEM location. However, the IE downpipe is a two-piece unit, and IE puts the cat between the downpipe and midpipe connection. Of the two, the IE will likely have superior flow because of the larger diameter of the single pipe, as well as the placement of the cat further downstream. It is also much cheaper, and you can get the full two-piece downpipe/midpipe combo for cheaper than the Unitronic downpipe alone. 

For those interested in only upgrading the midpipes, we have two options: the Unitronic RS3 MidPipes and the CTS Turbo RS3 MidPipes. Both of these designs are completely catless and will bolt up to either the stock downpipe and cat-back or most aftermarket units. 

6) RS3 Cold Air Intake and Turbo Inlet

For our final RS3 mod, we suggest upgrading the air intake and turbo inlet. The air intake is the first part of the intake system, and draws in air to feed to the turbo. While the OEM intake and airbox is adequate for a completely stock car, once you start tuning and adding other mods it becomes completely overmatched. Upgrading to a higher flowing intake will eliminate any restriction and add 15-25 horsepower with tuning. 

The turbo inlet sits between the air intake and the turbo and connects them. Like the airbox, the OEM inlet is a bit restrictive, and can really impede horsepower and torque once you start modding. With an upgraded turbo inlet, you can see an additional 10-20 horsepower with tuning. 

Best RS3 Intakes and Turbo Inlets

For the RS3 intake upgrades, the top options are the Iroz Motorsport RS3 High Flow Intake and the IE RS3 Cold Air Intake. Both of them are solid options, with the main difference being the airbox and scoop. The IE unit comes with an integrated carbon fiber airbox and scoop that draws in cold air from directly under the hood. The Iroz intake is a completely open filter intake with no airbox or scoop. The IE intake will allow for a little better performance, but it’s also a $400 price difference. 

For the turbo inlet, the top options are the Eventuri RS3 Turbo Inlet or the Unitronic RS3 Turbo Inlet. Both of them will perform similarly, and the main difference is the material. The Eventuri inlet uses carbon fiber while the Unitronic is made from aluminum. The carbon fiber will weigh a little bit less and will also be superior for heat reduction, but both are solid options. 

Top Audi RS3 Mods FAQ

What is the best Audi RS3 mod?

The 6 best Audi RS3 mods are upgraded intercooler, ECU/TCU tuning/piggyback, E85 and Flex-fuel tuning, upgraded downpipe/midpipes, dogbone mount and bushing, and upgraded air intake and turbo inlet. With these mods, you can make more than 500 wheel-horsepower on the Audi RS3 on the stock turbo.

How much horsepower can the Audi RS3 make after modding?

With Stage 1 mods, the Audi RS3 can make roughly 475-500 horsepower and 450-500 lb-ft of torque, and Stage 1+ is 500-525 horsepower and 475-515 lb-ft of torque. Stage 2 is roughly 550 horsepower and 525 lb-ft of torque. Adding ethanol will easily show gains of an additional 75-100 horsepower and 100-150 lb-ft of torque on top. With a Stage 2 tune and ethanol, you can expect to make roughly 500 wheel-horsepower with the RS3.

Is the Audi RS3 a good engine to mod?

Yes, the 2.5 TFSI inside the Audi RS3 is a fantastic engine for modding. With the right mods, you can pump out more than 500 wheel-horsepower on the RS3 with the stock turbo. 

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